Telephone systems come in a variety of "sizes." Although the term "size" in the context of a telephone system can have many definitions, one way to gauge the "size" of a telephone system is to identify the number of telephone lines and/or telephone sets that the system can support. For example, there are versions of the "DEFINITY.RTM." PBX (available from Lucent Technologies Inc.) that support thousands of lines and/or thousands of telephone sets. Similarly, at the other end of the spectrum, there are telephone systems, such as the PARTNER.RTM. Communications System (available from Lucent Technologies Inc.) that provide cost effective telecommunications solutions in which only a single telephone line and a few telephone sets are required.
However, regardless of size, one characteristic of a telephone system remains unchanged. There is always a central control point. In large systems, this may be a computer comprising a number of circuit boards for a central processing unit, memory, etc. Such a computer provides a telecommunications-specific operating system for allocating system resources and controlling communications. On the other hand, in small systems, this central control point may be provided by a telephone set designated as a "master" or "key system unit" (KSU). This KSU controls other satellite telephone sets in the system. As such, when additional equipment is added to the system, this additional equipment is "administered" in some fashion by the KSU.
An example of a system having a "master unit" is described in U.S. Pat. No. 4,807,225, issued Feb. 21, 1989 to Fitch and entitled "Telephone Line Carrier System." It should be noted that this system provides a telephone apparatus that creates additional communication channels (via radio-frequency (RF) channels) at a business or residential premises and is compatible with existing telephone extensions that share a common wire-pair.
Alternatively, U.S. Pat. No. 4,757,496, issued Jul. 12, 1988 to Bartholet et al. and entitled "Distributed Telephone System" describes a telephone system without a central control point where each telephone set is coupled to a coaxial cable via a control unit. Unfortunately, this system still requires either a fixed administration, or manual programming, to set some system parameters such as telephone set addresses.